Far-field optical microscope with a nanometer-scale resolution based on the in-plane image magnification by surface plasmon polaritons

ABSTRACT

A far-field optical microscope capable of reaching nanometer-scale resolution using the in-plane image magnification by surface plasmon polaritons is presented. The microscope utilizes a microscopy technique based on the optical properties of a metal-dielectric interface that may, in principle, provide extremely large values of the effective refractive index n eff  up to 10 2 -10 3  as seen by the surface plasmons. Thus, the theoretical diffraction limit on resolution becomes λ/2n eff , and falls into the nanometer-scale range. The experimental realization of the microscope has demonstrated the optical resolution better than 50 nm for 502 nm illumination wavelength.

PRIORITY

This application claims priority under 35 U.S.C. §119(e) to a U.S.Provisional Application filed on Feb. 20, 2004 and assigned U.S.Provisional Application No. 60/546,146 and to a U.S. ProvisionalApplication filed on May 7, 2004 and assigned U.S. ProvisionalApplication No. 60/569,305; the contents of both applications areincorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with government support under NSF contract nos.ECS-0210438 and ECS-0304046 awarded by the National Science Foundation.The government has certain rights in this invention.

BACKGROUND OF THE INVENTION

1. Technical Field

The disclosure relates to optical microscopy. In particular, thedisclosure relates to a far-field optical microscope with ananometer-scale resolution based on the in-plane image magnification bysurface plasmon polaritons.

2. Description of the Prior Art

Far-field optical microscopy remains invaluable in many fields ofscience, even though various electron and scanning probe microscopeshave long surpassed it in resolving power. The main advantages of thefar-field optical microscope are the ease of operation and direct samplevisualization. Unfortunately, the resolution of a regular opticalmicroscope is limited by the wavelength of visible light. The reason forthe limited resolution is diffraction and, ultimately, the uncertaintyprinciple: a wave can not be localized much tighter than half of itsvacuum wavelength λ/2.

Immersion microscopes introduced by Ernst Abbe in the 19th century haveslightly improved resolution on the order of λ/2n because of the shorterwavelength of light λ/n in a medium with refractive index n. However,immersion microscopes are limited by the small range of refractiveindices n of available transparent materials. It was believed that theonly way to achieve nanometer-scale spatial resolution in an opticalmicroscope is to beat diffraction, and detect evanescent optical wavesin very close proximity to a studied sample using a scanning near-fieldoptical microscope. Although many fascinating results are obtained withnear-field optics, such microscopes are not as versatile and convenientto use as regular far-field optical microscopes. For example, an imageof a near-field optical microscope is obtained by point-by-pointscanning, which is an indirect and a rather slow process.

However, it has been realized that a dielectric droplet on a metalsurface which supports propagation of surface plasmons (or surfaceplasmon polaritons) may have an extremely large effective refractiveindex as seen by these modes (see I. I. Smolyaninov, Surface plasmontoy-model of a rotating black hole, New Journal of Physics, vol. 5,pages 147.1-147.8, October 2003, the contents of which are incorporatedherein by reference). The properties of surface plasmons and convenientways to excite them are described in detail in H. Raether, SurfacePlasmons, Springer Tracts in Modern Physics, vol. 111, Springer, Berlin,1988.

Accordingly, it is an aspect of the present disclosure to describe afar-field optical microscope capable of reaching nanometer-scaleresolution using the in-plane image magnification by surface plasmonpolaritons based on the optical properties of a metal-dielectricinterface that may provide extremely large values of the effectiverefractive index n_(eff) up to 10³ as seen by surface polaritons, andthus the diffraction limited resolution can reach nanometer-scalevalues.

SUMMARY OF THE INVENTION

The present disclosure describes a far-field optical microscope capableof reaching nanometer-scale resolution using the in-plane imagemagnification by surface plasmon polaritons, also known astwo-dimensional light, which is made of electromagnetic waves coupledwith conducting electrons. The immersion microscope of the presentdisclosure improves resolution using an approach based on the opticalproperties of a metal-dielectric interface that may provide extremelylarge values of the effective refractive index n_(eff) up to 10³ as seenby surface polaritons. Thus, the diffraction limited resolution canreach nanometer-scale values of λ/2n_(eff). The experimental realizationof such an immersion microscope has demonstrated the optical resolutionbetter than 50 nm at 502 nm illumination wavelength.

The microscopy technique employed by the immersion microscope of thepresent disclosure improves resolution without expensive equipment andspecial preparations needed for electron microscopes and othertechnologies. The microscopy technique entails coaxing plasmonpolaritons into magnifying images by placing a microscopic sample onto athin, coated glass surface (such as a meta-coated glass surface thatsupports propagation of surface electromagnetic waves), like a documenton the surface of a photocopier, and depositing a drop of glycerin orother substance on top of it. Alternatively, instead of depositing adrop of glycerin or other substance, a solid parabolically shapeddielectric layer can be provided on the metal surface. Laser light isthen propagated or shined through the glass creating surface plasmonpolaritons in the metal-coating. The plasmon polaritons “sense” thesample by scattering off of it. They can sense finer details thanordinary light because their wavelength is only 70 nm, seven timesshorter than that of the laser.

To concentrate the scattered two-dimensional light, the curved verticalsurface of the glycerin drop where the light contacts the metallic planeand reflects plasmon polaritons is used. This vertical surface(metal-dielectric interface) works a bit like a giant radio telescopedish in reverse: rather than focusing parallel astronomical light raysto a point, it collects the scattered plasmon polaritons emerging fromthe sample and redirects them as a plasmon beam along the metallicplane. To view the image, nanoscale irregularities in the metal surfacescatter some of the light of the beam upward, so that an ordinarymicroscope objective can catch the image and be viewed through at leastone lens of the microscope positioned for viewing the image propagatedby the scattered beam. The droplet's shape is adjusted “by hand” usingmicromanipulators, such as a probe.

BRIEF DESCRIPTION OF THE FIGURES

These and other advantages will become more apparent from the followingdetailed description of the various embodiments of the presentdisclosure with reference to the figures wherein:

FIG. 1(a) is a schematic illustration of a surface plasmon immersionmicroscope where surface plasmons are excited by laser light andpropagate inside a parabolic-shaped droplet and the placing of a samplenear the focus of a parabola produces a magnified image in the metalplane in accordance with the present disclosure;

FIG. 1(b) is a graph illustrating Ar-ion laser line positions withrespect to the dispersion curve of plasmons on the gold-glycerineinterface shown in FIG. 1(a), and the approximate locations of otherguided optical modes inside the thin layer of glycerine;

FIG. 2 illustrates the dispersion laws of surface plasmons and normalphotons propagating inside the dielectric (shown in FIG. 1(a)) at smallangles along the metal-dielectric interface, where the k-axis representsthe quasi-momentum of the respective electromagnetic mode and theintersections between the modes are shown by the dots;

FIG. 3(a) illustrates an exponentially decaying surface plasmon beamemitted from an artificial pinhole in a 50 nm thick gold film immersedin a thin glycerin droplet stained with the bodipy die;

FIG. 3(b) is a graph illustrating a cross-section of the beam shown inFIG. 3(b);

FIG. 3(c) illustrates an image undergoing the effect of mode couplingdue to the slowly varying shape of the glycerin droplet, where quicklydecaying surface plasmon beams emitted by two pinholes give rise toweaker guided mode beams, which exhibit much longer propagation length;

FIG. 3(d) is a graph illustrating a cross-section of the image shown inFIG. 3(c);

FIG. 3(e) is a schematic illustrating how the mode coupling effect mayconserve angular resolution;

FIG. 4(a) is a photograph showing the formation of glycerin droplets indesired locations on the metal film by bringing a small probe wetted inglycerin into close proximity to a sample;

FIG. 4(b) is a photograph showing glycerin microdroplet formation inlocations indicated by the arrows by bringing the probe to a surfaceregion covered with glycerin;

FIGS. 5(a)-5(f) show images of a 30×30 μm² rectangular nanohole arraywith 500 nm hole spacing formed in various droplets;

FIGS. 6(a)-6(f) show images of a resolution test of the microscope inaccordance with the present disclosure;

FIG. 7(a) is a graph illustrating image magnification measured in thesurface plasmon image of a triplet nanohole array along the line shownin the inset, which is parallel to the optical axis of the droplet andwhere the dots in the graph show the distance between the neighbouringtriplets in the image as a function of the triplet position measuredalong the optical axis;

FIG. 7(b) is a chart illustrating the cross-section through the line ofdouble holes in the image of the triplet nanohole array shown in FIG.7(a);

FIGS. 8(a) and 8(b) respectively illustrate electro microscope andplasmon microscope images of the gaps in the 30×30 μm² periodic nanoholearray;

FIG. 8(c) is a schematic illustration of the theoretical ray-opticsreconstruction of the image shown in FIG. 8(b);

FIG. 8(d) is a graph illustrating a cross-section of the plasmon imageobtained along the line shown in FIG. 8(b); and

FIG. 9 illustrates images and data generated during an evaluation of themicroscope designed in accordance with the present disclosure at aresolution of 502 nm.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present disclosure describes a far-field optical microscope capableof reaching nanometer-scale resolution using the in-plane imagemagnification by surface plasmon polaritons based on the opticalproperties of a metal-dielectric interface that may provide extremelylarge values of the effective refractive index n_(eff) up to 10³ as seenby surface polaritons, and thus the diffraction limited resolution canreach nanometer-scale values.

I. Introduction

The wave vector of a surface plasmon propagating over an interfacebetween a dielectric and an infinitely thick metal film is defined bythe expression $\begin{matrix}{k_{p} = {\frac{\omega}{c}\left( \frac{ɛ_{d}ɛ_{m}}{ɛ_{d} + ɛ_{m}} \right)^{\frac{1}{2}}}} & (1)\end{matrix}$where ε_(m)(ω) and ε_(d)(ω) are the frequency-dependent dielectricconstants of the metal and dielectric, respectively. If the imaginarypart of the metal's dielectric constant is neglected, under the resonantconditionε_(m)(ω)=−ε_(d)(ω)   (2)both phase and group velocities of the surface plasmons tend to zero.This means that the wavelength λ_(p) of such plasmons becomes very smalljust below the optical frequency defined by equation (2), or in otherwords, the effective refractive index of the dielectric n_(eff) becomesextremely large as seen by the propagating surface plasmons in thisfrequency range. As a result, a small droplet of liquid dielectric,e.g., glycerin, on the metal surface, e.g., gold film, becomes a verystrong lens for surface plasmons propagating through the droplet fromthe outside. On the other hand, the droplet boundary becomes anextremely efficient mirror for surface plasmons propagating inside thedroplet at almost any angle of incidence due to the total internalreflection (this leads to the “black hole” analogy described in I. I.Smolyaninov, Surface plasmon toy-model of a rotating black hole, NewJournal of Physics, vol. 5, pages 147.1-147.8, October 2003).II. Surface Plasmon Immersion Microscope

The above-described realization has led to the introduction of a surfaceplasmon immersion microscope 10 as described below with reference to thefigures.

Let us consider a far-field two-dimensional optical microscope made ofdielectric droplets 12 as shown in FIG. 1(a). Since the wavelength ofsurface plasmons 4, observed in the STM light emission (see I. I.Smolyaninov, V. S. Edelman, and V. V. Zavyalov, Spectroscopicmeasurements of light emitted by the STM, Phys. Letters A, vol. 158,pages 337-340, 1991) and near-field optical experiments (see H. J. Maas,J. Heimel, H. Fuchs, U. C. Fischer, J. C. Weeber, and A. Dereux,Photonic nanopatterns of gold nanostructures indicate the excitation ofsurface plasmon modes of a wavelength of 50-100 nm by scanningnear-field optical microscopy, Journal of Microscopy, vol. 209, pages241-248, 2002) may be as small as a few nanometers (hencen_(eff)=λ/λ_(p) may reach extremely large values up to 10²), thediffraction limit of resolution of such a two-dimensional microscope mayapproach λ_(p)/2 or λ/2n_(eff). Theoretically, it may reach a scale of afew nanometers.

If a sample 14 under investigation is forced to emit propagating surfaceplasmons using laser illumination 16, or if it is illuminated bypropagating plasmons, these plasmons may produce a two-dimensionalmagnified image 18 of the sample 14 in the appropriate location on ametal surface 20 placed on a glass prism 22 or other similar opticaldevice. The metal surface 20 as shown in FIG. 1(a) is a gold film. Othermetallic and non-metallic coatings can be used to coat a top surface ofthe glass prism 22 in accordance with the present disclosure, such assilver, copper, aluminum, semiconductors, other types of metals, andother film material which supports surface electromagnetic wavepropagation.

Because of the metal surface roughness and the Raleigh scattering in thedielectric droplet 12 (the dotted line in FIG. 1(a) indicates thedroplet's optical axis), the propagating plasmons are constantlyscattered into normal photons propagating in free space. As a result,the plasmon-produced far-field two-dimensional image 18 on the metalsurface 20 may be visualized by through a normal optical microscopeobjective 24. The image brightness far exceeds the background ofscattered plasmons in other areas of the two-dimensional microscope, andin addition, a fluorescence scheme of surface plasmon fieldvisualization by a far-field optical microscope may be used (see H.Ditlbacher, J. R. Krenn, G. Schider, A. Leitner, and F. R. Aussenegg,Two-dimensional optics with surface plasmon polaritons,Appl.Phys.Letters, vol. 81, pages 1762-1764, 2002).

The dielectric droplet 12 is preferably a glycerin droplet. However, anyliquid dielectric droplet can be used in accordance with the presentdisclosure. Additionally, instead of using a liquid dielectric droplet,a solid parabolically shaped dielectric layer can be provided on themetal surface 20 and used as a lens and/or mirror for surface plasmonsin accordance with the present disclosure.

The exact coupling efficiency between the plasmon-produced image 18 andphotons in free space which may be collected by a regular microscopedepends on the surface roughness and/or the type of fluorescent dye usedin the microscope. A typical surface plasmon resonance linewidthmeasured in the experiment is in the 1-10% range (see H. Raether,Surface Plasmons, Springer Tracts in Modern Physics, vol. 111, Springer,Berlin, 1988), which indicates plasmon to photon conversion efficiencydue to surface roughness of about the same order of magnitude. About thesame conversion efficiency has been observed in the fluorescent imagingexperiment (see Ditlbacher et al.). In addition, this couplingefficiency may be improved by introducing an artificial periodiccorrugation of the metal surface (however, such an artificial surfacecorrugation may cause difficulties in distinguishing real objects fromthe patterns produced by periodic corrugation).

Thus, the goal of a two-dimensional microscope design is to havesufficiently high two-dimensional image magnification, so that all thetwo-dimensional image details would be larger than the λ/2 resolutionlimit of the normal optical microscope. As a result, a far-field opticalmicroscope with nanometer-scale resolution is produced in accordancewith the present disclosure and as described herein and reported in I.I. Smolyaninov, J. Elliott, A. V. Zayats, and C. C. Davis, Far-fieldoptical microscope with nanometer-scale resolution, received by Phys.Rev. Letters on Mar. 10, 2004, the contents of which are incorporatedherein by reference. Experimental proofs of the microscope's resolutionof at least 50 nm, which is equal to approximately λ/10 and farsupersedes resolution of any other known far-field optical microscope,have been demonstrated and presented. The microscopy technique inaccordance with the present disclosure is believed will lead to numerousbreakthroughs in biological imaging and sub-wavelength lithography.

However, the theoretical description of the microscope given abovepresents an oversimplified picture of the microscope operation. Forexample, the imaginary part of the metal's dielectric constant severelylimits the shortest attainable surface plasmon wavelength and thesurface-plasmon propagation length in most cases. This in turn limitsthe microscope's two-dimensional magnification in the metal plane.Herein is described how these limitations have been overcome in theexperiment, and provide an analysis regarding the practical limits onthe surface plasmon microscope resolution. In addition, experimentalresults are presented which strongly support the conclusion of extremelyhigh spatial resolution of the surface plasmon microscope of the presentdisclosure.

III. Shortest Wavelength of a Surface Plasmon

The amplitude of every resonance in nature is limited by the energylosses. The same statement is valid with respect to the surface plasmonresonance. It is clear from eq. (1) that the imaginary part of ε_(m)(ω)limits the shortest attainable wavelength of surface plasmons on aninfinitely thick metal film. Given the assumption that ε_(d) is real,while ε_(m)=ε^((r)) _(m)+iε^((i)) _(m), the shortest wavelength of asurface plasmon would be equal to $\begin{matrix}{\lambda_{P\quad\min} = {\lambda\left( {- \frac{2ɛ_{m}^{(i)}}{ɛ_{d}ɛ_{m}^{(r)}}} \right)}^{\frac{1}{2}}} & (3)\end{matrix}$In the frequency range of the Ar-ion laser lines (which corresponds tothe plasmon resonance at the gold-glycerin interface reported in I. I.Smolyaninov, J. Elliott, A. V. Zayats, and C. C. Davis, Far-fieldoptical microscope with nanometer-scale resolution, received by Phys.Rev. Letters on Mar. 10, 2004) this value could not be much smaller then200 nm. Thus, the idealized surface plasmon dispersion curve shown inFIG. 1(b) has nothing to do with reality if the gold film is very thickand glycerin is used as a dielectric.

However, the situation changes radically if the gold film thicknessfalls into the few tens of nanometers range, and the dielectric constantof the substrate used for the gold film is chosen to coincide with thedielectric constant of the liquid droplet on the gold film surface. Insuch a case, a pair of surface plasmon modes appears (the symmetric andthe antisymmetric solutions of the Maxwell equations), and in the largewave vector limit the surface plasmon dispersion in eq.(1) is modifiedto look as follows: $\begin{matrix}{{k_{p} = {\frac{\omega}{c}\left( \frac{ɛ_{d}ɛ_{m}}{ɛ_{d} + {ɛ_{m} \pm {2ɛ_{d}{\mathbb{e}}^{{- k_{p}}d}}}} \right)^{\frac{1}{2}}}},} & (4)\end{matrix}$where d is the gold film thickness. The term 2ε_(d)e^(−k) ^(p) ^(d) inthe denominator of eq. (4) has real and imaginary parts, so that byplaying with the frequency and the gold film thickness the plasmonmomentum may be forced to diverge in the case of the antisymmetricplasmon mode (see J. J. Burke, G. I. Stegeman, and T. Tamir,Surface-polariton-like waves guided by thin, lossy metal films, Phys.Rev. B, vol. 33, pages 5186-5201, 1986.

As a result, the use of an idealized surface plasmon dispersion curveshown in FIG. 1(b) is justified for a finite thickness of the gold filmin a situation in which the dielectric constants of the droplet and thesubstrate are close to each other. Thus, glycerin with the refractiveindex of n_(gl)=1.47 is ideally suited for experiments performed withgold films deposited onto a glass substrate. It is noted that the use ofmaterials with larger dielectric constants in the visible range (such asdiamond or semiconductors) would improve the situation even for thethicker gold films (and make it more close to an ideal) since this wouldshift the plasmon resonance towards longer wavelengths where the ε^((i))_(m) falls very rapidly.

IV. Extending the Surface Plasmon Propagation Length

While the use of idealized surface plasmon dispersion curve in FIG. 1(b)for glycerin droplets has been justified in the previous section, evenmore crucial question for the consideration of the far-field surfaceplasmon microscope performance is the surface plasmon propagationlength. The importance of this question may again be illustrated in thecase of infinitely thick metal film. For a complex ε_(m) the imaginarypart of k_(p) from eq. (1) determines the surface plasmon propagationlength L_(p). Around λ_(Pmin) the propagation length becomes extremelyshort: L_(p)˜2λ_(Pmin), and it is clear that a far-field surface plasmonmicroscope could not be built in this case.

However, it appears that the use of symmetric geometry may again help toovercome the surface plasmon propagation problem. The effect of dramaticenhancement of the surface plasmon propagation length over a thin metalfilm in the symmetric configuration has been described previously byBurke et al. in J. J. Burke, G. I. Stegeman, and T. Tamir,Surface-polariton-like waves guided by thin, lossy metal films, Phys.Rev. B, vol. 33, pages 5186-5201, 1986. According to their calculations,the plasmon propagation over a symmetric structure appears to betypically an order of magnitude larger compared to the case of anasymmetric structure. For example, a surface plasmon propagation atλ=633 nm over a 15 nm thick silver film surrounded on both sides by adielectric with refractive index 1.5 may reach 610 micrometers.Moreover, Burke et al. had found two additional leakysurface-plasmon-like solutions in the thin film geometry and noted thatsuch leaky modes may even grow in intensity with distance under theresonant excitation if the rate of energy influx from the excitationsource is greater than the dissipation in metal.

Here we should point out that in our experiments, as reported in I. I.Smolyaninov, J. Elliott, A. V. Zayats, and C. C. Davis, Far-fieldoptical microscope with nanometer-scale resolution, received by Phys.Rev. Letters on Mar. 10, 2004, a substantial portion of surface plasmonpropagation occurs over the areas of gold films which were perforated bythe periodic arrays of nanoholes. It is clear that all the surfaceplasmon-like modes, which propagate over a periodically corrugated goldsurface must be leaky modes due to the photonic crystal effects.

The dispersion laws of surface plasmons and normal photons propagatinginside the dielectric at small angles along the metal-dielectricinterface are shown in FIG. 2, where k represents the quasi-momentum ofthe respective electromagnetic mode. Since each branch (photon orplasmon) of the dispersion law can be shifted along the k-axis by aninteger number of the inverse lattice vectors, it is clear that thesebranches have an infinite number of intersections with each other. Theseintersections are shown by the dots in FIG. 2.

Irrespective of the nature of the periodic corrugation (nanoholes likein our experiments, or something else), the propagation length ofsurface-plasmon-like modes drastically changes near these intersectionpoints. According to the observation by Burke et al., plasmonpropagation length near the intersection points between the dispersionlaws of plasmon-like modes and photons in the dielectric should increasedramatically. The physical reason for this effect may be understood asthough plasmons spend some of their lifetime as regular photons, andthus, propagate much farther. On the other hand, under the resonantexcitation plasmon-like leaky modes which propagate over a periodicsurface may even grow in intensity if the rate of energy influx from theexcitation source is greater than the dissipation in metal. It ispointed out that the vast majority of the intersection points in FIG. 2are located in the large wave vectors area of the unperturbed plasmondispersion curve, which is exactly the property needed for highresolution microscopy. Thus, while the exact values of surface plasmonpropagation length over a periodic nanohole array need to be calculatedfrom the first principles, there exist good reasons for this propagationlength to be large over the nanohole array for short-wavelengthplasmons.

In order to achieve the best possible magnification of the plasmonmicroscope, both effects of the plasmon propagation length increasedescribed above should be used: the preferred geometry of thetwo-dimensional microscope according to the present disclosure should bebased on a thin periodically corrugated metal film surrounded on bothsides by dielectric media with equal dielectric constants. The resultsof the measurements of surface plasmon propagation length shown in FIG.3 and described in detail in Section VI confirm substantial increase ofthe surface plasmon propagation length in a symmetric configurationchosen in our experiments.

V. The Role of Mode Coupling

Liquid droplets with large-enough thickness may support not only thesurface plasmons at the metal-dielectric interface but regular guidedmodes as well (FIG. 1(b)). These guided modes are similar to theelectromagnetic modes that propagate in dielectric waveguides. Thedroplet profile changes with distance along its optical axis: ideallythe droplet has a parabolic shape in the xy-plane, and in addition, thedroplet thickness varies in the z-direction. Far from the droplet edgesboth the droplet thickness and the droplet width vary slowly, whichleads to weak coupling between all the electromagnetic modes of thesystem due to momentum non-conservation (because of the loss oftranslation symmetry along the metal plane). This effect has beenobserved in our experiments (see FIG. 3(c, d) and detailed discussion inSection VI).

The diffraction-limited angular resolution ˜λ_(p)/F of the microscopeaccording to the present disclosure is defined by the plasmonpropagation around the focal point of the parabolic mirror/droplet,where F is the focal length of the mirror and λ_(p) is the plasmonwavelength. Once the short-wavelength surface plasmons left the area inthe vicinity of the focal point, and reached some more distant area ofthe droplet with a larger width D>>F, plasmon conversion into the guidedmodes with larger wavelength λ_(g) may not lead to the deterioration ofthe angular resolution (see the sketch in FIG. 3(e)). If λ_(p)/F˜λ_(g)/Dangular resolution of the microscope will be conserved. After such aconversion, the two-dimensional image formed by the propagation of theguided modes will keep all the spatial information which would becontained in a plasmon-formed image if the plasmons would reach thegeometrical location of the image. This statement is true as long as thegeometrical optics description of the mode propagation inside thedroplet remains valid, or if λ_(g)<<F. Thus, the mode coupling effectprovides another way of solving the problem of short plasmon propagationlength, which has been discussed in the previous section.

Based on the discussion above, the best shape of the dielectric dropletseems to be a compound shape, which may be approximated by two parabolassuch that the focal length of the first parabola is much smaller thanthe focal length of the second one. In this case the role of theparameter D is played by the focal length of the second parabola, andthe short-wavelength plasmons need to travel only a distance of theorder of the focal length F of the first one. Such a compound dropletshape has been used in some of the experiments described below.

VI. New Experimenal Evidence of Enhanced Resolution

In a scheme similar to one described in I. I. Smolyaninov, Surfaceplasmon toy-model of a rotating black hole, New Journal of Physics,vol.5, pages 147.1-147.8, October 2003, glycerin microdroplets have beenused as two-dimensional optical elements in the design of the plasmonmicroscope in accordance to the present disclosure. The dielectricconstant of glycerin ε_(g)=2.161 is ideally suited for experimentsperformed on a gold surface within the wavelength range of the laserlines of an argon-ion laser (FIG. 1(b)). At the λ₀=502 nm line, the realpart of the gold dielectric constant is ε_(m)=−2.256.

According to equation (1), the corresponding surface plasmon wavelengthinside glycerin is λ_(p)˜70 nm, and the effective refractive index ofglycerin is n_(eff)=λ₀/λ_(p)˜7. On the other hand, the use of glycerinachieves good dielectric constant matching with the silica glass, whichhas been used as a substrate for the gold films. According to thediscussion above, this fact is important for improving surface plasmonpropagation over the gold films with the thickness in the 50-100 nmrange used in our experiments.

The plasmon propagation length over the gold-glycerin interface at 502nm has been measured using two complementary techniques: near-fieldimaging technique described in I. I. Smolyaninov, Surface plasmontoy-model of a rotating black hole, New Journal of Physics, vol. 5,pages 147.1-147.8, October 2003 and Smolyaninov, I. I., Mazzoni, D. L.,and Davis, C. C., Imaging of surface plasmon scattering bylithographically created individual surface defects, Phys. Rev. Letters,vol., 77, pages 3877-3880, 1996; and the fluorescent surface plasmonimaging technique similar to the one described in H. Ditlbacher, J. R.Krenn, G. Schider, A. Leitner, and F. R. Aussenegg, Two-dimensionaloptics with surface plasmon polaritons, Appl. Phys. Letters, vol. 81,pages 1762-1764. 2002. Both techniques gave similar results.

In our experiments artificial pinholes in gold film were produced insidea thin glycerin droplet (which was stained with the bodipy dye) bytouching the gold film with a sharp STM tip. Such pinholes are known toemit propagating surface plasmon beams. The characteristic exponentiallydecaying surface plasmon beam (excited from the right side of the image)observed in this experiment is shown in FIG. 3(a), which has beenobtained using fluorescent imaging. The cross-section of this beam shownin FIG. 3(b) has been fitted by an exponent and indicates plasmonpropagation length of the order of 3 micrometers at 502 nm laserwavelength. In some cases it was possible to image the process ofsurface plasmon coupling into the regular guided modes described inSection V, as shown in FIGS. 3(c, d). Image (c) and its cross-section(d) show the effect of mode coupling due to the slowly varying shape ofthe glycerin droplet: quickly decaying surface plasmon beams emitted bytwo pinholes give rise to weaker guided mode beams, which exhibit muchslower decay and longer propagation length.

In the microscopy experiments the samples were immersed inside glycerindroplets on the gold film surface. The droplets were formed in desiredlocations by bringing a small probe FIG. 4(a) wetted in glycerin intoclose proximity to a sample. The probe was prepared from a taperedoptical fiber, which has an epoxy microdroplet near its apex. Bringingthe probe to a surface region covered with glycerin led to a glycerinmicrodroplet formation under the probe (FIG. 4 b). The size of theglycerin droplet was determined by the size of the seed droplet ofepoxy. The glycerin droplet under the probe can be moved to a desiredlocation under the visual control, using a regular microscope.

Our droplet deposition procedure allowed us to form droplet shapes,which were reasonably close to parabolic. In addition, the liquiddroplet boundary may be expected to be rather smooth because of thesurface tension, which is essential for the proper performance of thedroplet boundary as a two-dimensional plasmon mirror. Thus, the dropletboundary was used as an efficient two-dimensional parabolic mirror forpropagating surface plasmons excited inside the droplet by externallaser illumination. Since the plasmon wavelength is much smaller thanthe droplet sizes, the image formation in such a mirror can be analyzedby simple geometrical optics in two dimensions.

Periodic nanohole arrays first studied by Ebbesen et al. (see T. W.Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff,Extraordinary optical transmission through sub-wavelength hole arrays,Nature, vol. 391, pages 667-669, 1998) appear to be ideal test samplesfor the plasmon microscope of the present disclosure. Illuminated bylaser light, such arrays produce propagating surface waves, whichexplains the anomalous transmission of such arrays at opticalfrequencies. FIG. 5 shows various degrees of two-dimensional imagemagnification obtained with a 30×30 μm² rectangular nanohole array with500 nm hole spacing described in A. V. Zayats, I. I. Smolyaninov, W.Dickson, and C. C. Davis, Polarization superprism effect in surfacepolaritonic crystals, Appl. Phys. Letters vol. 83, pages 4438-4440, 2003and used as a test sample.

In general, smaller glycerine droplets produced higher magnification inthe images. It should be pointed out that all the guided modes in thedroplet (surface plasmons and the regular guided modes shown in FIG.1(b)) participate in the formation of the two-dimensional images. Therelative contribution to the image of each mode changes with distancefrom the imaged sample due to varying mode coupling and decay.Approximate reconstructions of the images using two-dimensionalgeometrical optics (via ray tracing) are shown next to each experimentalimage. If the shape of the two-dimensional mirror (the droplet edge) isgiven by the exact parabolic dependence as Y=X²/2P, the point (X₁, Y₁)is reflected into the point (X₂, Y₂) according to the followingexpressions: $\begin{matrix}{x_{2} = {{- \frac{P}{x_{1}}}\left( {\sqrt{\left( {y_{1} - \frac{P}{2}} \right)^{2} + x_{1}^{2}} - \left( {y_{1} - \frac{P}{2}} \right)} \right)}} & (5) \\{y_{2} = {{\left( {\frac{P^{2}}{2x_{1}^{2}} - \frac{1}{2}} \right)\left( {\sqrt{\left( {y_{1} - \frac{P}{2}} \right)^{2} + x_{1}^{2}} - \left( {y_{1} - \frac{P}{2}} \right)} \right)} + \frac{P}{2}}} & (6)\end{matrix}$These expressions are precise. However, the droplet shapes in ourexperiments may only approximately be represented by parabolas, and thedamping of surface plasmon field over varying propagation lengths hasnot been included in the simulation (extensive sets of data on theplasmon propagation length versus the plasmon frequency and the metaland dielectric film thicknesses can be found in Burket et al.). Thesefacts limit the precision of our image reconstructions.

Nevertheless, we achieved a significant qualitative agreement betweenthe experimental and theoretical images of the plasmon microscopeaccording to the present disclosure. In all the calculated imagesdescribed below the individual nanoholes of the arrays are shown asindividual dots in the theoretical images. Comparison of FIG. 5(c) andFIG. 5(d) indicates that the rows of nanoholes separated by 0.5 μm mayhave been resolved in the image (c) obtained using only a 10× objectiveof the conventional microscope, while comparison of FIG. 5(e) and FIG.5(f) obtained using a 50× objective indicates that individual 150 nmdiameter nanoholes separated by 0.5 μm gaps are resolved in the image(e) obtained at 502 nm. These individual nanoholes are located in closeproximity to the focus of the droplet/mirror, and hence experience thehighest image magnification. In fact, the image in FIG. 5(e) showssuccessful use of the droplet with compound parabolic geometry describedin the end of the previous section, which is supposed to take the fulladvantage of the mode coupling mechanism described in section V.

Even though the exact role of mode coupling in formation of each imagein FIG. 5 is not clear, it seems certain that the two-dimensional imagesin FIGS. 5(a, c) are formed with considerable participation of theguided modes, since the distance travelled by the electromagnetic modesis of the order of 100 micrometers in these cases. While the image inFIG. 5(a) does not contain any evidence of high resolution, the image inFIG. 5(c) seems to demonstrate that the mode coupling does preserve highangular and spatial resolution, as has been discussed in section V.

Another resolution test of the microscope of the present disclosure hasbeen performed using a 30×30 μm² array of triplet nanoholes (100 nm holediameter with 40 nm distance between the hole edges) shown in FIG. 6(c).This array was imaged using a glycerine droplet shown in FIG. 6(a). Theimage of the triplet array obtained at 515 nm using a 100× microscopeobjective is shown in FIG. 6(b) (compare it with an image in (d)calculated using the two-dimensional geometrical optics). Although theexpected resolution of the microscope at 515 nm is somewhat lower thanat 502 nm, the 515 nm laser line is brighter, which allowed for theobtainment of more contrast in the two-dimensional image. Theleast-distorted part of the image 6(b) (far from the droplet edge, yetclose enough to the nanohole array, so that surface plasmon decay doesnot affect resolution) is shown at higher digital zooms of the CCDcamera mounted onto a conventional optical microscope in FIGS. 6(e, f).These images clearly visualize the triplet nanohole structure of thesample.

According to the geometrical optics picture of the two-dimensionalplasmon microscope operation, its magnification M is supposed to growlinearly with distance along the optical axis of the droplet/mirror:$\begin{matrix}{{M = {\frac{2y}{P} - 1}},} & (7)\end{matrix}$where P is the focal distance of the parabola. Our measurements of theimage magnification indeed exhibit such linear dependence (FIG. 7 a).The dots in the graph show the distance between the neighbouringtriplets in the image as a function of triplet position measured alongthe optical axis of the droplet. At small distances individual nanoholesare not resolved within the triplet. At larger distances (where thetriplets are resolved, see the cross section in FIG. 7(b) measuredthrough the line of double holes in the image of the triplet array, thedata points represent the positions of the triplet's centres. The gap inthe data corresponds to the intermediate area of the image in which thefeature identification in the image is difficult. The slope of themeasured linear dependence in FIG. 7(a) corresponds to P=7 μm, which isin reasonable agreement with the value of P of the order of 10 μm, whichcan be determined from the visible droplet dimensions in FIG. 6(a).

While the simple geometrical optics model of the image formation agreesreasonably well with the experiment, a few alternative mechanisms mayform an image of a periodic source, such as the Talbot effect (see I. I.Smolyaninov, and C. C. Davis, On the nature of apparent“superresolution” in near-field optical microscopy, Optics Letters, vol.23, pages 1346-1347, 1998). However, resolution of the Talbot imagesalso approximately equals to λ/2n. Thus, whatever optical mechanism isinvolved in the formation of the images of the triplets in FIG. 6,short-wavelength plasmons are necessarily involved in this mechanism.

In addition, reconstruction of the source image in the Talbot effecthappens at the specific planes where exact field distribution of thesource is reproduced. These planes are called the Talbot planes. At allthe distances, other then the set of Talbot distances, the pattern ofillumination differs greatly from the pattern of the source: instead oftriad features of the source, one may see sets of 6, 9, 12, etc. brightillumination maxima. This diffraction behavior is further complicated bythe fact that different triads of the source are located at differentdistances from a given triad of the image. Since it is very hard toimagine that the periodicity of the source would exactly coincide withthe periodicity of the Talbot planes spacing, the mechanism of imageformation due to diffraction effects seems highly improbable. At thesame time, all the diffraction and interference phenomena reproduce thegeometrical optics description in the limit of small wavelengths. Thisfact is reflected in rather good agreement between the experimentalimages and the images calculated in the geometrical opticsapproximation.

In order to prove that the plasmon microscope is capable of aperiodicsamples visualization, we have obtained images of small gaps in theperiodic nanohole arrays (FIG. 8). The electron microscope image of oneof the gaps in the periodic array of nanoholes is shown in FIG. 8(a).Two wider mutually orthogonal gaps were made in the array along bothaxis of the structure as shown in the theoretical reconstruction in FIG.8(c). The plasmon image in FIG. 8(b) and its cross-section in FIG. 8(d)obtained at 502 nm wavelength shows both the periodic nanohole structureand the gap in the structure indicated by the arrows in the images. Thewidth of the gap in the image grows linearly with the distance from thesample in agreement with the measurements in FIG. 7. In principle, theobserved gap in the image might be interpreted as a Moire pattern, dueto two shifted diffraction patterns from the two portions of thenanohole array separated by the gap.

However, the cross-section through the gap in the image (FIG. 8 d) maybe considered as evidence against such interpretation. Dark stripes inthe Moire patterns normally exhibit slightly attenuated brightnesscompared to the original overlapping illumination patterns. The contrastin the image between the gap and the images of nanoholes seems to be toolarge for a Moire pattern interpretation.

Finally, in order to evaluate the microscope resolution at the optimized502 nm wavelength, the cross-sections of the images of the tripletstructure (similar to the one described earlier in FIG. 6) obtained atthis wavelength were analyzed. The most magnified triplets, which arestill discernible in the experimental image in FIG. 9(a) are shown bythe arrow (compare this image with the theoretical one shown in FIG.9(b)). These triplets are shown at a higher zoom in FIG. 9(c). Thecross-section through two individual nanoholes in the triplet clearlyshows the 40 nm gap between the nanoholes. While optical properties ofthis particular triplet may slightly differ from the designed values andlead to an appearance of a wider gap in the image, the distance betweenthe centres of the nanoholes should be 140 nm. The cross-section in FIG.9(c) seems to indicate at least three times better resolution of theplasmon microscope of about 50 nm. Thus, at least 50 nm (λ/10) spatialresolution of the microscope is clearly demonstrated. This high spatialresolution is consistent with the estimated 70 nm wavelength of surfaceplasmons at 502 nm.

Theoretical resolution of such microscope may reach the scale of a fewnanometers, since only the Landau damping at plasmon wave vectors of theorder of the Fermi momentum seams to be capable of limiting the smallestpossible plasmon wavelength. However, increasing resolution may putadditional extremely stringent requirements on the quality of the edgeof the dielectric microdroplet/mirror used in the microscope and on thesurface roughness of the metal substrate. In order to avoid imagebrightness loss due to plasmon scattering, the edge of the dielectricmirror should be smooth on a scale that is much smaller than thewavelength of the plasmons used. Surface tension of a viscous liquidmitigates this problem to some degree. However, enhancement of theoptical resolution down to 10 nm scale may require novel technicalsolutions.

Nevertheless, the surface plasmon microscope in accordance with thepresent disclosure has the potential to become an invaluable tool inmedical and biological imaging, where far-field optical imaging ofindividual viruses and DNA molecules may become a reality. It allowsvery simple, fast, robust and straightforward image acquisition. Waterdroplets on a metal surface could be used as elements of two-dimensionaloptics in measurements where aqueous environment is essential forbiological studies (however, the use of water droplets may present somedifficulties since change of dielectric media would require differentmatching conditions with the substrate, and water might not form equallyparabolic and stable droplets as glycerin). It is also pointed out thatif used in reverse, surface plasmon immersion microscope may be used innanometer-scale optical lithography. Both of these developments wouldpotentially revolutionize their respective fields.

VII. Conclusion

In conclusion, the present disclosure describes a far-field opticalmicroscope capable of reaching nanometer-scale resolution using thein-plane image magnification by surface plasmon polaritons, also knownas two-dimensional light, which is made of electromagnetic waves coupledwith conducting electrons. The immersion microscope of the presentdisclosure improves resolution using an approach based on the opticalproperties of a metal-dielectric interface that may provide extremelylarge values of the effective refractive index n_(eff) up to 10³ as seenby surface polaritons. Thus, the diffraction limited resolution canreach nanometer-scale values of λ/2n_(eff). The experimental realizationof such an immersion microscope has demonstrated the optical resolutionbetter than 50 nm at 502 nm illumination wavelength.

The microscopy technique employed by the immersion microscope of thepresent disclosure improves resolution without expensive equipment andspecial preparations needed for electron microscopes and othertechnologies. The microscopy technique entails coaxing plasmonpolaritons into magnifying images by placing a microscopic sample onto athin, coated glass surface (such as a meta-coated glass surface thatsupports propagation of surface electromagnetic waves), like a documenton the surface of a photocopier, and depositing a drop of glycerin orother substance on top of it. Alternatively, instead of depositing adrop of glycerin or other substance, a solid parabolically shapeddielectric layer can be provided on the metal surface. Laser light isthen propagated or shined through the glass creating surface plasmonpolaritons in the metal coating. The plasmon polaritons “sense” thesample by scattering off of it. They can sense finer details thanordinary light because their wavelength is only 70 nm, seven timesshorter than that of the laser.

To concentrate the scattered two-dimensional light, the curved verticalsurface 26 (see FIG. 1(a)) of the glycerin drop 12 where the light 16contacts the metallic plane 28 and reflects plasmon polaritons is used.This vertical surface 26 (metal-dielectric interface) works a bit like agiant radio telescope dish in reverse: rather than focusing parallelastronomical light rays to a point, it collects the scattered plasmonpolaritons emerging from the sample 14 and redirects them into a plasmonbeam along the metallic plane 28. To view the image, nanoscaleirregularities in the metal surface scatter some of the light of thebeam upward, so that an ordinary microscope objective 24 can catch theimage and be viewed through at least one lens 30 of the microscopepositioned for viewing the image propagated by the scattered beam. Thedroplet's shape is adjusted “by hand” using micromanipulators, such as aprobe. It is envisioned to replace this step with solid mirrors etchedon the glass by lithography.

The described embodiments of the present disclosure are intended to beillustrative rather than restrictive, and are not intended to representevery embodiment of the present disclosure. Various modifications andvariations can be made without departing from the spirit or scope of thedisclosure as set forth in the following claims both literally and inequivalents recognized in law.

1. A method for microscopy imaging using surface plasmon polaritons,said method comprising the steps of: placing an object to be imaged ontoa coated surface of a glass; depositing a dielectric droplet on theobject forming a vertical surface where the dielectric droplet contactsa plane of the coated surface; directing light through the glass forcreating surface plasmon polaritons in the coated surface which scatteroff the object, where the scattered plasmon polaritons are collected atthe vertical surface and redirected as a beam propagating an image ofthe object, where the beam is scattered by irregularities in the coatedsurface; and positioning at least one lens for viewing the imagepropagated by the scattered beam.
 2. The method according to claim 1,wherein the beam is propagated along the plane of the coated surface. 3.The method according to claim 1, further comprising the step ofadjusting the shape of the dielectric droplet using a micromanipulator.4. The method according to claim 1, wherein the dielectric droplet is aglycerin droplet.
 5. The method according to claim 1, wherein the coatedsurface is coated with a coating selected from the group consisting ofmetallic coatings, non-metallic coatings, and semiconductor coatings. 6.The method according to claim 1, wherein the at least one lens is a lensof an optical microscope.
 7. A method for microscopy imaging usingsurface plasmon polaritons, said method comprising the steps of: placingan object to be imaged onto a surface; depositing a dielectric dropleton the object forming a vertical surface where the dielectric dropletcontacts a plane of the surface; illuminating the object with plasmonpolaritons which scatter off the object, where the scattered plasmonpolaritons are collected at the vertical surface and redirected as abeam propagating an image of the object, where the beam is scattered byirregularities in the surface; and positioning at least one lens forviewing the image propagated by the scattered beam.
 8. The methodaccording to claim 7, wherein the beam is propagated along a plane ofthe surface and the surface is a coated surface of a glass.
 9. Themethod according to claim 8, wherein the coated surface is coated with acoating selected from the group consisting of metallic coatings,non-metallic coatings, and semiconductor coatings.
 10. The methodaccording to claim 7, further comprising the step of adjusting the shapeof the dielectric droplet using a micromanipulator.
 11. The methodaccording to claim 7, wherein the dielectric droplet is a glycerindroplet.
 12. The method according to claim 7, wherein the at least onelens is a lens of an optical microscope.
 13. A method formicroscopically imaging an object, said method comprising the steps of:placing the object onto a coated surface of a glass; depositing adielectric droplet on the object forming a dielectric-coated surfaceinterface where the dielectric droplet contacts a plane of the coatedsurface; and directing light through the glass having a predeterminedfrequency which substantially corresponds to the plasmon resonance atthe dielectric-coated surface interface for exciting surface plasmonpolaritons at the dielectric-coated surface interface, said surfaceplasmon polaritons scatter off the object, are collected at thedielectric-coated surface interface and redirected as a beam propagatingan image of the object, where the beam is scattered by irregularities inthe coated surface.
 14. A surface immersion microscopy system forimaging an object using surface plasmon polaritons, said microscopysystem comprising: a glass positioned at one end of the objective, saidglass having a coated surface for placement of the object thereon andfor depositing a dielectric droplet on the object forming a verticalsurface where the dielectric droplet contacts a plane of the coatedsurface; a light source for propagating light through the glass forcreating surface plasmon polaritons in the coating which scatter off theobject, where the scattered plasmon polaritons are collected at thevertical surface and redirected as a beam propagating an image of theobject, where the beam is scattered by irregularities in the coatedsurface; and an objective having at least one lens positioned above theglass for viewing the image propagated by the scattered beam.
 15. Themicroscopy system according to claim 14, wherein the beam is propagatedalong a plane of the coated surface.
 16. The microscopy system accordingto claim 14, further comprising a micromanipulator for adjusting theshape of the dielectric droplet.
 17. The microscopy system according toclaim 14, wherein the dielectric droplet is a glycerin droplet.
 18. Themicroscopy system according to claim 14, wherein the coated surface iscoated with a coating selected from the group consisting of metalliccoatings, non-metallic coatings, and semiconductor coatings.
 19. Asurface immersion microscopy system for imaging an object using surfaceplasmon polaritons, said microscopy system comprising: a surface forplacement of the object thereon and for depositing a dielectric dropleton the object forming a vertical surface where the dielectric dropletcontacts a plane of the surface; a plasmon polariton source forilluminating the object with plasmon polaritons which scatter off theobject, where the scattered plasmon polaritons are collected at thevertical surface and redirected as a beam propagating an image of theobject, where the beam is scattered by irregularities in the coatedsurface; and an objective having at least one lens positioned above thesurface for viewing the image propagated by the scattered beam.
 20. Themicroscopy system according to claim 19, wherein the beam is propagatedalong a plane of the surface and the surface is a coated surface of aglass.
 21. The microscopy system according to claim 20, wherein thecoated surface is coated with a coating selected from the groupconsisting of metallic coatings, non-metallic coatings, andsemiconductor coatings.
 22. The microscopy system according to claim 19,further comprising a micromanipulator for adjusting the shape of thedielectric droplet.
 23. The microscopy system according to claim 19,wherein the dielectric droplet is a glycerin droplet.
 24. The microscopysystem according to claim 19, wherein the resolution provided by saidmicroscopy system is at least 50 nm for 502 nm illumination wavelengthof said propagated light.
 25. A method for microscopy imaging usingsurface plasmon polaritons, said method comprising the steps of: placingan object to be imaged onto a coated surface of a glass, said coatedsurface having a dielectric thereon forming a dielectric-coated surfaceinterface where the dielectric contacts a plane of the coated surface;creating surface plasmon polaritons in the coated surface which scatteroff the object and are collected at the dielectric-coated surfaceinterface and redirected as a beam propagating an image of the object,where the beam is scattered by irregularities in the coated surface; andpositioning at least one lens for viewing the image propagated by thescattered beam.
 26. The method according to claim 24, wherein thedielectric is selected from the group consisting of a liquid dielectricand a solid dielectric.
 27. The method according to claim 24, whereinthe coated surface is coated with a coating selected from the groupconsisting of metallic coatings, non-metallic coatings, andsemiconductor coatings.
 28. A method for microscopy imaging usingsurface plasmon polaritons, said method comprising the steps of: placingan object to be imaged onto a surface having a dielectric thereonforming a dielectric-surface interface where the dielectric contacts aplane of the surface; illuminating the object with plasmon polaritonswhich scatter off the object, where the scattered plasmon polaritons arecollected at the dielectric-surface interface and redirected as a beampropagating an image of the object, where the beam is scattered byirregularities in the surface; and positioning at least one lens forviewing the image propagated by the scattered beam.
 29. The methodaccording to claim 28, wherein the dielectric is selected from the groupconsisting of a liquid dielectric and a solid dielectric.
 30. The methodaccording to claim 28, wherein the coated surface is coated with acoating selected from the group consisting of metallic coatings,non-metallic coatings, and semiconductor coatings.
 31. A surfaceimmersion microscopy system for imaging an object using surface plasmonpolaritons, said microscopy system comprising: a glass positioned at oneend of the objective, said glass having a coated surface for placementof the object thereon and a dielectric forming a vertical surface wherethe dielectric contacts a plane of the coated surface; a light sourcefor propagating light through the glass for creating surface plasmonpolaritons in the coating which scatter off the object, where thescattered plasmon polaritons are collected at the vertical surface andredirected as a beam propagating an image of the object, where the beamis scattered by irregularities in the coated surface; and an objectivehaving at least one lens positioned above the glass for viewing theimage propagated by the scattered beam.
 32. The microscopy systemaccording to claim 31, wherein the dielectric is selected from the groupconsisting of a liquid dielectric and a solid dielectric.
 33. Themicroscopy system according to claim 31, wherein the coated surface iscoated with a coating selected from the group consisting of metalliccoatings, non-metallic coatings, and semiconductor coatings.
 34. Asurface immersion microscopy system for imaging an object using surfaceplasmon polaritons, said microscopy system comprising: a surface forplacement of the object thereon and having a dielectric forming avertical surface where the dielectric contacts a plane of the surface; aplasmon polariton source for illuminating the object with plasmonpolaritons which scatter off the object, where the scattered plasmonpolaritons are collected at the vertical surface and redirected as abeam propagating an image of the object, where the beam is scattered byirregularities in the coated surface; and an objective having at leastone lens positioned above the surface for viewing the image propagatedby the scattered beam.
 35. The microscopy system according to claim 34,wherein the dielectric is selected from the group consisting of a liquiddielectric and a solid dielectric.
 36. The microscopy system accordingto claim 34, wherein the coated surface is coated with a coatingselected from the group consisting of metallic coatings, non-metalliccoatings, and semiconductor coatings.